We shall continue to apply spectrofluorometric methods to the analysis of protein conformation, protein-small molecule interactions, and protein-protein interactions. The main emphasis will be to use fluorescence spectroscopy and microscopy in conjunction with detailed chemical and cytological analyses in order to characterize the surface membrane complex of the mammalian cells. We will attempt to corroborate and refine our hypothesis on the mechanisms of control of receptor movement by cytoplasmic structures of the surface modulating assembly. These studies will include the characterization of macromolecules by various methods including fluorescence spectroscopy, application of fluorescence probes to analysis of the dynamics and interactions of macromolecular assemblies, and the development of instrumentation and techniques for quantitative fluorescence microscopy of individual cells.